Internal combustion engine

ABSTRACT

The internal combustion engine comprises at least one combustion chamber ( 1, 1 ′) for burning a fuel in timed explosions accompanied by formation of a combustion gas, at least one expansion chamber ( 3 ) which is connected with the combustion chamber and separate from the combustion chamber and which has a piston ( 4 ) for converting energy of the combustion gas into mechanical energy or work, and a cam gear unit by which a drive shaft ( 32 ) can be driven by the piston and which has a cam disk ( 31 ) and associated thrust member ( 30 ), wherein the thrust member ( 30 ) can be lifted from the cam disk ( 31 ) for carrying out irregular engine cycles independent from a continuous rotation of the cam disk ( 31 ), including a pausing of the piston ( 4 ) of the expansion chamber ( 3 ) at its top dead center.

[0001] The invention is directed to an internal combustion engine withat least one combustion chamber for burning a fuel in timed explosionsaccompanied by formation of a combustion gas, wherein the combustionchamber is connected with at least one expansion chamber which isseparate from the combustion chamber and which has a piston forconverting energy of the combustion gas into mechanical energy or work.Further, the invention is directed to a method for operating an internalcombustion engine of this type.

[0002] An engine of the kind mentioned above is known from EP 957 250A2. The advantage of an engine of this type with separate combustionchamber and expansion chamber is that the conditions for the combustionof the fuel and for the expansion of the combustion gas formed duringcombustion can be predetermined independently from one another, so thata high degree of efficiency can be achieved. A further improvement inefficiency compared with conventional two-stroke, four-stroke or dieselengines is achieved in this known engine in that, for each explosionstroke, the combustion chamber is filled with a constant, optimal chargeof combustible mixture. To control the power output of the engine, thecharging of the combustion chamber is not changed; rather, idle strokesare also inserted between working strokes in which the combustiblemixture is ignited in the combustion chamber. There is no ignition ofthe mixture in these idle strokes; the mixture remains unburned in thecombustion chamber. In order to make it possible to transmit the driveoutput of an engine controlled in this manner to a drive shaft, forexample, of a wheel in a motor vehicle, relatively complicated steps arenecessary in EP 957 250 A2. In an embodiment example, the piston of theexpansion chamber is connected with a connecting rod which drives thedrive shaft via an automatic transmission which is controlled inaccordance with the required output and the required torque. In thisregard, there is considerable expenditure on control and, moreover,lateral forces are exerted on the piston by the crankshaft, so that oillubrication of the piston is required. In another embodiment example inEP 957 250 A2, the piston of the expansion chamber advantageouslyremains in an idle stroke at its top dead center. A hydraulictransmission device which, again, is relatively complicated is necessaryfor transmitting the drive output.

[0003] It is the object of the invention to enable simplifiedtransmission of the output of the piston of the expansion chamber to adrive shaft in an internal combustion engine of the type mentioned inthe beginning, wherein idle strokes or stroke pauses in which the pistonof the expansion chamber remains in its top dead center can be insertedin addition to working strokes in order to control the engine(preferably with constant loading of the combustion chamber) such thatefficiency is optimized. This highly complex problem is solved accordingto the invention in a surprisingly simple manner in that a drive shaftcan be driven by the piston of the expansion chamber via a cam drive orcam gear unit having a cam disk and associated thrust member, whereinthe thrust member can be lifted from the cam disk for implementingirregular engine cycles independent from a continuous rotation of thecam disk, including a pausing of the piston of the expansion chamber atits top dead center.

[0004] Cam gear units have a cam disk with a correspondingly shapedcircumferential contour and (as driving or driven element) a thrustmember contacting the cam disk. A cam gear unit of this kind enables asimple separation of the piston of the expansion chamber from the driveshaft during an idle stroke or stroke pause when a running face of a camdisk is provided for the thrust member only on one side and the thrustmember remains raised from the cam disk during the idle stroke or strokepause. The thrust member is advantageously formed by the free end of thepiston rod which, for this purpose, is advantageously constructed as aroller tappet acting on a cam disk arranged at the drive shaft. The useof a cam disk also makes it possible to operate the internal combustionengine without oil lubrication for the piston (as will be explained inmore detail).

[0005] For internal combustion engines which do not belong to thegeneric type because they do not have an expansion chamber that isseparate from a combustion chamber but, rather, have a work piston thatis arranged directly in the combustion chamber, the use of special camgear units has already been suggested in particular, for example, inU.S. Pat. No. 5,813,372. However, this cam gear unit is used for otherpurposes and not to make it possible to add idle strokes between twoexplosion strokes; idle strokes of this type cannot be carried out atall in this kind of engine. Further, in these internal combustionengines, the thrust members of the cam gear units are positively guidedbecause of the cam disks acting on both sides of the thrust members andit is not possible to raise the thrust member from the cam disk. Since aseparate compression stroke must be carried out in these engines, thispositive guiding of the thrust rod is required.

[0006] In a preferred embodiment example of the invention, aprecompressor device which is separated from the combustion chamber isprovided for precompression of air to be introduced into the combustionchamber. Using separate precompressor devices in this way in timedinternal combustion engines is already known, for example, from DE 32 14516 A1. In a particularly preferred embodiment example, the piston rodof the piston of the precompressor device is connected with the pistonof the expansion chamber by a shared piston rod.

[0007] Further, at least one injection nozzle opening into the expansionchamber is advantageously provided for injecting a coolant liquid tointroduce an implosion stroke following the explosion stroke. The energyinherent in the combustion gas can be better exploited by an implosionstroke of this kind so that a further increase in efficiency isachieved. The energy guided off in the implosion stroke isadvantageously utilized for precompression by transmission to theprecompressor device.

[0008] Further advantages and details of the invention are explained inthe following with reference to an embodiment example of the inventionshown in the drawing.

[0009]FIG. 1 shows a schematic top view of an internal combustion engineaccording to the invention;

[0010]FIG. 2 shows a section along line A-A of FIG. 1;

[0011]FIG. 3 shows a partial section along line B-B of FIG. 1;

[0012]FIG. 4 shows a partial section along line C-C of FIG. 1;

[0013]FIG. 5 shows a schematic view of a cam disk of the cam gear unit;and

[0014]FIG. 6 shows a schematic view of an embodiment form in which aplurality of units, each with an expansion chamber and a connecting rod,act on a shared cam disk.

[0015] The embodiment example of an internal combustion engine accordingto the invention which is shown schematically has combustion chambers 1,1′ which are connected, via controllable internal combustion chamberoutlet valves 2, 2′, with an expansion chamber 3 which is formed by thecylinder space of a piston-cylinder unit 5 having a piston 4. Aninternal combustion engine according to the invention can also have aplurality of expansion chambers which are connected with one or morecombustion chambers.

[0016] The combustion chambers 1, 1′ are surrounded by thermalinsulation 6 in order to prevent heat radiation from the walls 7 of thecombustion chambers 1, 1′ as far as possible. Therefore, in continuousoperation of the internal combustion engine the walls 7 of thecombustion chambers 1, 1′ are heated to very high temperatures above700° C. The thermal insulation of the combustion chambers could also becarried out in that the combustion chambers themselves are made from athermally insulating material of corresponding thickness, for example, aceramic. The fuel is injected directly into the combustion chambers 1,1′. For this purpose, double nozzles 8, 8′ are provided and are used notonly to inject fuel but also serve to inject water. The spraycharacteristic of the double nozzles 8, 8′ is such that the fuel fansout so that the walls 7 of the combustion chambers 1, 1 are wetted byfuel as well as possible and over the greatest possible area when fuelis injected. An electromagnetic switching valve 9 is provided forcontrolling the fuel injection, and a pressure accumulator 10 for fuelin the form of an air vessel which is acted upon by a fuel pump 11which, in turn, conveys fuel from a tank 12 is connected to thiselectromagnetic switching valve 9. The reference switching time for theelectromagnetic switching valve 9 is in the range of one millisecond.Such electromagnetic switching valves are known in motor vehicles (forexample, K-Jettronic or Common Rail).

[0017] Spark plugs 13, 13′ are provided for cold-starting the internalcombustion engine. As soon as the walls 7 of the combustion chambers 1,1′ are sufficiently heated and autoignition of the injected fuel occurs(at temperatures over approximately 600° C.), the spark plugs 13, 13′are no longer fired. Because of its autoignition, the fuel is finelyatomized by the injection nozzles at high pressure and introduced intothe combustion chamber only at the moment of ignition. When theindividual fuel droplets impinge, they ignite at the burner walls withflame centers around each individual droplet.

[0018] Because of the flame center occurring around each individualdroplet as a result of the multiple surface ignitions, there is apronounced knock of the engine, i.e., the combustion proceeds withextreme turbulence and at high speed. In contrast to conventionalinternal combustion engines in which this effect is extremelyundesirable (prevention through antiknock agent and limited compressionratios), this type of combustion is very advantageous in the engineaccording to the invention since, in particular, the turbulence of thecombustion with supersonic gas eddies leads to an intensive mixing ofthe mixture during burnup. This already makes possible air factors oflambda 1.05 for approximately CO-free and HC-free burnup, wherein valuesfar below the exhaust gas value of an Otto engine with catalyticconverter can be achieved. Due to the fact that the gas transfer causedby pressure is faster than the flame speed during burnup, the combustionchamber outlet valve 2 remains closed until complete combustion of themixture because otherwise unburned mixture reaches the work chamber 3and no longer ignites therein.

[0019] In order to minimize thermal losses in the piston-cylinder unit 5also as far as possible, the insulation 6 also extends over the cylinderhead 14. In addition, the piston 4 is provided with insulation 15. Onlythe cylinder wall 16 is not thermally insulated in order to preventexcessive thermal loading of the piston seal 17. This piston seal 17 ismade of plastic, preferably graphite-Teflon, which is resistant tocontinuous temperatures up to approximately 250° C. This seal 17 iswater-lubricated and one or more coolant water spray nozzles which arearranged in the piston rod 18 and whose function will be described moreexactly in the following cause an additional cooling and a lubricationof the piston seal 17.

[0020] In order to reduce NOx emission of the internal combustionengine, water is injected into the combustion chambers 1, 1′ along withthe fuel during the explosion stroke. This water injection is likewisecarried out via double nozzles 8, 8′. For this purpose, each of thedouble nozzles 8, 8′ has a central inner nozzle for injecting the fueland an outer nozzle which surrounds this inner nozzle annularly forinjection of water. The nozzle opening of the inner fuel nozzle and thenozzle opening of the water nozzle are closed in pressureless state andonly open when these nozzles are acted upon by a high pressure such asis known in conventional diesel nozzles. At its circumferential wall,the outer water nozzle has a water inlet and a water outlet locatedopposite to the latter, wherein coolant water flows through this waternozzle also in the closed state of its nozzle opening, so that the innerfuel nozzle is also cooled and no fuel can evaporate when the walls 7 ofthe combustion chambers 1, 1′ are hot but no explosion stroke is carriedout and the engine is at rest. The flow of water through the outer waternozzle of the double nozzle 8, 8′ is caused by the pump 11 which pumpswater from a storage vessel 20. An electromagnetic valve 21 is providedin the return of the outer water nozzle of the double nozzle 8, 8′. Assoon as this is closed, a pressure builds up in the outer water nozzleof the double nozzle 8, 8′ and water is injected into the combustionchamber 1, 1′. When the valve 21 is open, the water flows back to thestorage vessel 20 via the spray head 22 and the air intake head 23 whosefunction will be described in more detail in the following.

[0021] The piston 4 of the expansion chamber 3 is connected with aprecompressor device which is formed by a piston-cylinder unit 25. Thepiston 24 of this piston-cylinder unit and the piston 4 of the expansionchamber 3 have a shared piston rod 18. During a downward movement of thepiston 4 which is transmitted via the piston rod 18 to a downwardmovement of the piston 24, air is sucked into the cylinder space of thepiston-cylinder unit 25 via the check valve 26. The quantity of airsucked in before reaching the bottom dead center of the piston 4 can bechanged by means of the throttle 27 which is adjustable via theactuating motor 28. In a subsequent upward movement of piston 4 andpiston 24 of the precompressor unit, which piston 24 is connected topiston 4, the sucked in air is pressed into the combustion chambers 1,1′ via the check valves and is precompressed therein.

[0022] The energy of the hot combustion gas which is formed in thecombustion chambers 1, 1′ and which drives the piston 4 in the expansionchamber 3 is converted into mechanical energy of the drive shaft 32 bymeans of a cam gear unit 31 which can be driven by the piston 4. Thethrust member 30 of the cam gear unit is formed by the free end of thepiston rod 18 of the piston 4 which, in the present embodiment example,forms the shared piston rod of the piston 4 of the expansion chamber andof the piston 24 of the precompressor unit. The thrust member 30 isconstructed as a roller tappet, wherein a wheel or a roller 33 isrotatably mounted via a ball bearing at the free end of the piston rod18. The thrust member 30 acts on a cam disk 31 arranged at the driveshaft 32 and the piston rod 18 is mounted outside the piston-cylinderunit 5 in a rolling bearing 34 which also receives the lateral forcesexerted on the thrust member 30. Accordingly, no important lateralforces are exerted on the upper part of the piston rod 18 and on thepistons 4 and 24 arranged at the latter, and simple O-shaped plasticseals 35, 17, 37 are sufficient for additional supporting and sealing ofthese parts. Oil lubrication of these parts is not required.

[0023] In the shown embodiment example, the cam disk 31 has twosymmetrically formed cams 38 along its circumference. The part of thecam disk 31 contacting the roller 33 during the downward movement of thepiston 4 forms a first running surface 39 of the cam disk 31. Further, asecond running surface 40 is preferably provided at the cam disk 31 fromwhich the piston 4 can be restored to its top dead center. However, aswill be described below, the force exerted on the piston 4 and piston24, respectively, via the second running surface 40 and thrust member 30is reinforced in the present embodiment example of the invention by theforce acting on the piston 4 in the implosion stroke and can even bereplaced by it.

[0024] A work cycle of the embodiment example of an internal combustionengine according to the invention will be described more exactly in thefollowing:

[0025] In continuous operation of the internal combustion engine, duringwhich the walls 7 of the combustion chambers 1, 1′ have a hightemperature, as was described, the ignition of the fuel injected intothe combustion chambers 1, 1′ which are charged with fresh air iscarried out by autoignition at the walls 7. The spark plugs 13, 13′ areutilized for ignition only in the startup phase. The injection andignition of the fuel is carried out at a point in time shortly beforethe first running surface 39 reaches the roller 33. During the nextmillisecond, the combustion spreads in the combustion chambers 1, 1′ andis essentially concluded when the tip of the cam 38 or the start of therunning surface 39 reaches the roller 33. The time period required forcomplete combustion depends, among other things, on the utilized fuel,the precompression of the fresh air in the combustion chambers 1, 1′ andthe burner shape and is, for example, about 3 milliseconds. Accordingly,in order to determine the correct injection and ignition times, thespeed and the angular position of the shaft 32 must be determined bysuitable sensors. Before the internal combustion engine is started, thecam disk 31 is brought into a position by the electric motor 41 so thatthe roller 33 contacts precisely the start of the first running surface39 in order to ensure the correct rotating direction of the drive shaft32 when starting. After the start of the internal combustion engine, theelectric motor 41 acts as a generator for supplying energy to theelectric components of the vehicle and for charging the vehicle battery.

[0026] In addition to injecting water into the combustion chambers 1, 1′during the explosion stroke together with the fuel for reducing NOxemissions, as was already mentioned, additional water is preferablysprayed into the combustion chambers 1, 1′ after complete burnup of thewater-fuel mixture at about 1500° C. for further reduction of thetemperature of the combustion gas. Accordingly, the temperature of thehot combustion gas is additionally reduced to below 1000° C., preferablyto below 900° C.; however, the required temperature of the walls 7 ofthe combustion chambers 1, 1′ is retained for autoignition of the fuel.Therefore, no change in exergy occurs in the hot combustion gas. Butafter the expansion, described below, of the gas-vapor mixture in theexpansion chamber 3 accompanied by performance of mechanical work, thisgas-vapor mixture only has temperatures of less than 300° C.Accordingly, all seals can be formed of maintenance-free plastic andmaintenance-intensive stop seals can be dispensed with.

[0027] When the roller 33 contacts the start of the running surface 39and the combustion in the combustion chambers 1, 1′ is essentiallycompletely terminated, the combustion chamber outlet valves 2, 2′ areopened and the hot combustion gas which is under pressure flows into theexpansion chamber 3 and propels the piston 4 downward. The pistonperforms work against the drive shaft 32 via the cam gear 30, 31. Bysuitable selection of the quantity of injected fuel and precompressedfresh air and with corresponding dimensioning of the combustion chambers1, 1′ in relation to the expansion chamber 3, the combustion gas hasexpanded to roughly atmospheric pressure when the piston 4 has reachedthe bottom dead center UT. The volume of the expansion chamber 3 isessentially greater than, preferably more than twenty-times greaterthan, the total volume of combustion chambers 1, 1′ communicating withthe expansion chamber 3.

[0028] The hot combustion gas preferably flows out of the combustionchambers 1, 1′ into the expansion chamber 3 so as to be throttled. Forthis purpose, the combustion chamber outlet valves 2, 2′ are openedgradually rather than suddenly with maximum speed. The line crosssections between the combustion chambers 1, 1′ and the expansion chamber3 can also be relatively small. The advantage in the hot combustiongases flowing out in a throttled manner is the reduced pressure peaksacting on the piston 4 and all parts connected therewith. Since thethrottling constitutes a rubbing of the gas, this results in heating ofthe gas. This increase in the temperature of the expansion gas leads toan increase in its volume and pressure. However, this gas has not yetperformed work in the internal combustion engine according to theinvention when flowing out of the combustion chambers 1, 1′, so that theexergy of the gas is not changed by this throttling effect, i.e., nolosses occur.

[0029] The explosion stroke is accordingly terminated and an implosionstroke is subsequently introduced in the present embodiment example ofthe invention, during which implosion stroke the combustion chambers 1,1′ are scavenged and refilled and precompression is carried out. Forthis purpose, the cooling water injection nozzles 42 (a plurality ofinjection nozzles arranged annularly along the circumference of thepiston rod 18 or an individual annular injection nozzle) are triggeredby the actuation of the electromagnetic valve 43. The cooling waterinjection nozzles 42 are fed from a pressure accumulator 45 in the formof an air vessel which is acted upon by a pump 44. The pump 44 draws itswater from the storage vessel 20 which was already mentioned. Thecoolant water is sprayed in under high pressure, wherein the spray waterjet is fanned out in the circumferential direction of the cylinder wall16 and is oriented upward at an acute angle relative to the piston 4.Excess coolant water encountering the cylinder wall 16 can accordinglyexit in the circumferentially extending water collecting groove 47. Dueto the fact that coolant liquid is sprayed in, the temperature of thehot explosion gas is reduced suddenly and an underpressure or negativepressure is built up, wherein the pressure in the expansion chamber isapproximately 0.2 bar at the start of the implosion stroke. Because ofthis negative pressure, the piston 4 is pulled upward in the directionof the top dead center OT. The force exerted on it is transmitted viathe piston rod 35 to the piston 24 of the precompressor device. Thepiston 24 moving upward presses the fresh air stored in the cylinderspace of the piston-cylinder unit 25 into the combustion chambers 1, 1′via the check valves 29, 29′, so that the combustion gas is initiallypurged from the latter and is replaced by fresh air. At the conclusionof the charge exchange, which is also assisted by the negative pressurein the expansion chamber 3, the combustion chamber outlet valves 2, 2′are closed and increased pressure is subsequently built up in thecombustion chambers 1, 1′. This pressure preferably ranges between 5 barand 15 bar and is particularly preferably between 7 bar and 11 bar.

[0030] The spraying in of coolant liquid via the injection nozzles 42 iscarried out only in the first phase of the upward movement of the piston4 and is stopped before the injected coolant liquid would impinge on thehot cylinder head 14. The injected coolant liquid also serves to coolthe cylinder wall 16 and to lubricate the piston seal 36.

[0031] A spring 48 which pretensions the piston 24 in the direction ofits top dead center and is tensioned during the explosion stroke can beprovided to reinforce the force exerted on the piston 24 of theprecompressor unit by the implosion of the hot combustion gas. Thequantity of fresh air with which the piston-cylinder unit 25 is chargedduring the explosion stroke and which is subsequently pressed into thecombustion chambers 1, 1′ is controlled by the choke 27. In thisembodiment example, in which the piston 24 is pretensioned via thespring 48, the thrust member 30 is normally lifted from the respectivesecond running surface 40 at the cam disk 31 during the implosionstroke. Corresponding to the movement of the piston 4 from the top deadcenter to the bottom dead center which is faster in the explosion strokethan in the implosion stroke because of the negative pressure from thebottom dead center to the top dead center, the first running surface 39of the cam disk 31 extends over about 40° to 70° of the circumference ofthe cam disk, while the second running surface 40 extends over about110° to 140°. This second running surface 40 is provided here only as asafety device in case no cooling liquid is injected for triggering animplosion stroke due to a fault. The return speed of the piston 24 ismeasured electronically to regulate the throttle 27. It must be ensuredthat piston 24 or piston 4 has been braked precisely to a speed of zeroup to the top dead center and, on the other hand, that piston 24 orpiston 4 has just reached the top dead center. If an air cushionremained in the cylinder space of the piston-cylinder unit 25, thiswould exert a downwardly directed force on this piston 24 immediately atthe conclusion of the upward movement of the piston 24, i.e., in somecases before the opening of the combustion chamber outlet valves 2, 2′in the subsequent explosion stroke.

[0032] In order to minimize the time for damaging heat losses due toconvection, the first running surface 39, 39′ is constructed moresteeply than the second running surface 40, 40′.

[0033] Alternatively, however, the spring 48 can also be dispensed with.In this case, the upward movement of the piston 24 is reinforced by thecam disk 31 according to the standard. A cam disk 31′ constructed in amanner corresponding to FIG. 5 is preferred for this purpose. In thiscase, two cams, each with a first and second running surface 39′, 40′,are provided. The first running surface 39′ again has an angular rangeof approximately 40° to 70° of the circumference of the cam disk, whilethe angular range of the second running surface 40′ is somewhere between50° and 80°. The piston 4 or piston 24 is accordingly guided back in apositive or compulsory manner from the bottom dead center UT to the topdead center OT, wherein this process is still, as before, reinforced bythe force exerted on the piston 4 by means of the implosion. In order toprevent the connecting rod 30 from lifting off the running surface 40′at low rotational speeds also (for example, at speeds below 30 km/h inmotor vehicles), the injection of the coolant water is carried out in athrottled manner at these slow rotational speeds, so that the negativepressure forming in the implosion stroke is built up more gradually. Theprecompression pressure selected in this case is high enough to brakethe return of the piston 24 also at the maximum speed of the engine tothe top dead center to zero. Accordingly, there is no longer a need forelectronic measurement of the return speed or the associated regulatingelement in the form of the choke 27. In the cam disk in FIG. 5, there isa larger area 49 with constant radius between the successive runningsurfaces 40′ and 39′ in which the pistons 4 and 24 are at their top deadcenters, so that the ignition time for the combustion chambers 1, 1′receives a certain tolerance period and, in particular, a sufficientperiod of time is provided for complete adiabatic burnup of the mixturein the combustion chambers 1, 1′. The pause at the top dead center OTcan be adjusted over the length of the area 49 depending on thecombustion velocity of the utilized fuel.

[0034] In principle, it would be conceivable and possible to omitentirely an injection of coolant water for triggering an implosionstroke, wherein pistons 4 and 24 are displaced from their bottom deadcenter to the top dead center exclusively by the force exerted on thethrust member 30 via the running surface 40, 40′ of the cam disk 31,31′. Naturally, a certain reduction in efficiency of the internalcombustion engine is accordingly taken into account.

[0035] On its path from the bottom dead center to the top dead center,the piston 4 of the expansion chamber 3 further compresses thecombustion gas which is located in the expansion chamber 3 and which isinitially under negative pressure in case coolant liquid is sprayed in.During the movement of the piston 4 from its bottom dead center to thetop dead center, the ring 51 of the expansion chamber outlet valve isdisplaced upward. For this purpose, a plurality of restoring springs 52acting upward on the ring 51 are provided at the top of the cylinderhead 41 along the circumference of the ring 51 (see FIG. 4). Theserestoring springs 52 pull the ring 51 into its upper position in whichan annular outlet channel 53 is released when the tappets 55 arranged inthe hydraulic cylinders 54 are not under pressure load by the hydraulicliquid. A plurality of hydraulic cylinders 54 are likewise arranged onthe top side of the cylinder head 14 along the circumference of the ring51. O-rings 56, 57 which run alongside the ring 51 are used to seal thering 51. The seal 67 is provided for sealing the outlet channel 53 inthe bottom position of the ring 51. The ring 51 has a wedge-shaped taperat its lower edge to increase the sealing pressure.

[0036] When the ring 51 is displaced into its upper position releasingthe outlet channel 53, the expansion chamber outlet valve 50 is stillclosed by the O-ring 58 which surrounds the outlet channel 53 on theouter side and forms a check valve. When the pressure in the expansionchamber 3 has increased above atmospheric pressure during the upwardmovement of the piston 4 in the direction of the top dead center, theO-ring 59 releases the outlet channel 53 and the cooled combustion gas,together with the coolant liquid contained therein, is pressed out inthe exhaust pipe line 59. The exhaust gas-steam mixture is pressed intothe spray head 22 through which it is sprayed into the air intake funnel23. In so doing, the exhaust gas-steam mixture is mixed with surroundingair by a factor of 1:10 to 1:25 and is suddenly cooled to about 30° C.The cooled water precipitates in the precipitator 60. The fresh air issucked in by means of a suction fan 61 arranged downstream. The exhaustgas-cooling air mixture is separated via an exhaust 62, while theprecipitated coolant water is returned to the storage vessel 20.

[0037] When the piston 4 has reached its top dead center, a workingstroke of the internal combustion engine is concluded and the combustionchambers 1, 1′ are filled with precompressed fresh air. Depending on theinstantaneous output requirement, the next working stroke of theinternal combustion engine can either be initiated (by injection of fuelinto the combustion chambers 1, 1′) in that the combustion has concludedat a time at which the thrust member 30 has just reached the next firstrunning surface 39, 39′ or a stroke pause of varying length can beinserted. During this stroke pause, the piston 4 of the expansionchamber remains at its top dead center and the thrust element 30 islifted from the cam disk 31, while the cams 38 of the cam disk move pastthe thrust element 30 freely below the latter. The next working strokeof the internal combustion engine is introduced by injecting fuel intothe combustion chambers 1, 1′ at a time when the thrust element 30 islocated exactly at the start of a first running surface 39, 39′ of thecam disk 31 at the conclusion of combustion when the combustion chamberoutlet valves 2, 2′ are opened.

[0038] After the internal combustion engine has been stationary for alonger period of time, the above-atmospheric pressure of the fresh airlocated in the combustion chambers 1, 1′ has evaporated (due topersistent leakage in the valves). In this case, before starting theengine, a precompression of fresh air in the combustion chambers 1, 1′is carried out by the pump 64 driven by the motor 63 via lines withcheck valves 66, 66′. Further, the motor 41 brings the cam disk 31 intothe correct position in which the roller 33 is located at the start of afirst running surface 39, 39′. Subsequently, fuel is injected into thecombustion chambers and the mixture is ignited by the spark plugs 13,13′.

[0039] Instead of an individual unit 65 comprising the combustionchambers 1, 1′, expansion chamber 3 with piston 4, precompressor deviceand thrust element 30, it is also possible to provide two or more unitsof this kind which are controlled in a corresponding relationship to oneanother and act on the same cam disk or on a plurality of cam disks 31.For vibration-free running, units of this type are advantageouslyprovided in pairs so as to work in opposite directions. Gas movementsand mass movements accordingly cancel each other out. FIG. 6 shows aschematic view of an embodiment example in which four such units 65 acton an individual cam disk.

[0040] In the embodiment example shown in the drawing, the cam disk 31has two cams 38. In principle, it would also be conceivable and possibleto provide one cam 38 or more than two cams 38 of this kind.

[0041] In the shown embodiment example, the piston rod 18 is oriented atright angles to the drive shaft 32, In principle, it would also beconceivable and possible to provide the piston rod 18 and drive shaft 32with a parallel orientation and to provide the drive shaft 32 with a camdisk which is formed for a thrust element acting in axial direction ofthe drive shaft 32.

Reference Numbers

[0042]1,1′ combustion chamber

[0043]2,2′ combustion chamber outlet valve

[0044]3 expansion chamber

[0045]4 piston

[0046]5 piston-cylinder unit

[0047]6 thermal insulation

[0048]7 wall

[0049]8,8′ double nozzle

[0050]9 switching valve

[0051]10 pressure accumulator

[0052]11 fuel pump

[0053]12 tank

[0054]13,13′ spark plug

[0055]14 cylinder head

[0056]15 insulation

[0057]16 cylinder wall

[0058]17 piston seal

[0059]18 piston rod

[0060]19 pump

[0061]20 storage vessel

[0062]21 valve

[0063]22 spray head

[0064]23 air intake funnel

[0065]24 piston

[0066]25 piston-cylinder unit

[0067]26 check valve

[0068]27 throttle

[0069]28 actuating motor

[0070]29,29′ check valve

[0071]30 thrust member

[0072]31 cam disk

[0073]32 drive shaft

[0074]33 roller

[0075]34 rolling bearing

[0076]35 plastic seal

[0077]37 plastic seal

[0078]38 cam

[0079]39′ first running surface

[0080]40′ second running surface

[0081]41 electric motor

[0082]42 coolant water injection nozzle

[0083]43 valve

[0084]44 pump

[0085]45 pressure accumulator

[0086]47 water collecting groove

[0087]48 spring

[0088]49 area

[0089]50 expansion chamber outlet valve

[0090]51 ring

[0091]52 restoring spring

[0092]53 outlet channel

[0093]54 hydraulic cylinder

[0094]55 tappet

[0095]56 O-ring

[0096]57 O-ring

[0097]58 O-ring

[0098]59 exhaust line

[0099]60 precipitator

[0100]61 suction fan

[0101]62 exhaust

[0102]63 motor

[0103]64 pump

[0104]65 unit

[0105]66,66′ check valve

[0106]67 seal

1. Internal combustion engine with at least one combustion chamber (1,1′) for burning a fuel in timed explosions accompanied by formation of acombustion gas, at least one expansion chamber (3) which is connectedwith the combustion chamber and separate from the combustion chamber andwhich has a piston (4) for converting energy of the combustion gas intomechanical energy or work, and with a cam gear unit by which a driveshaft (32) can be driven by the piston and which has a cam disk (31) andassociated thrust member (30), wherein the thrust member (30) can belifted from the cam disk (31) for implementing irregular engine cyclesindependent from a continuous rotation of the cam disk (31), including apausing of the piston (4) of the expansion chamber (3) at its top deadcenter.
 2. Internal combustion engine according to claim 1 , wherein thethrust member (30) of the cam gear unit which acts on a cam disk (31)arranged at the drive shaft (32) is formed by the free end of the pistonrod (18) of the piston (4) of the expansion chamber (3) or by a partattached thereto and is constructed as a roller tappet.
 3. Internalcombustion engine according to claim 1 , wherein the cam disk (31) ofthe cam gear unit has two cams (38) along its circumference.
 4. Internalcombustion engine according to claim 1 , wherein a precompressor devicewhich is separated from the combustion chamber (1, 1′) is provided forprecompression of air to be introduced into the combustion chamber (1,1′).
 5. Internal combustion engine according to claim 4 , wherein theprecompressor device is formed by at least one piston-cylinder unit (25)whose piston (24) communicates mechanically with piston (4) of theexpansion chamber (3) and can be driven by a force acting on the piston(4) of the expansion chamber (3).
 6. Internal combustion engineaccording to claim 5 , wherein the piston (24) of the precompressordevice is pretensioned by a spring (48) in the position of its top deadcenter.
 7. Internal combustion engine according to claim 1 , wherein atleast one injection nozzle (42) opening into the expansion chamber (3)is provided for injecting a coolant liquid to introduce an implosionstroke following the explosion stroke, which injection nozzle ispreferably arranged in the shared piston rod (18) of the piston (4) ofthe expansion chamber (3) and of the piston (24) of the precompressordevice.
 8. Internal combustion engine according to claim 1 , wherein thepiston rod (18) of the piston (4) of the expansion chamber (3) ismounted via a rolling bearing (34).
 9. Internal combustion engineaccording to claim 1 , wherein the cam disk (31) has a first runningsurface (39, 39′) extending over 40° to 70° of the circumference of thecam disk for driving the cam disk (31) by means of the thrust member(30).
 10. Internal combustion engine according to claim 9 , wherein thecam disk (31) has a second running surface (40, 40′) for restoring thepiston (4) of the expansion chamber (3) to the top dead center (OT),which second running surface (40, 40′) preferably extends over 50° to140°, again preferably over 50° to 80° of the circumference of the camdisk (31).
 11. Internal combustion engine according to claim 10 ,wherein the first running surface (39, 39′) constructed more steeplythan the second running surface (40, 40′).
 12. Internal combustionengine according to claim 1 , wherein the cam disk (31) has an area (49)with a constant radius in which the piston (4) is located at its topdead center (OT), wherein the length of this area (49) corresponds atleast to the time required for the complete burnup of the mixture in thecombustion chamber at maximum rotational speed of the engine. 13.Internal combustion engine according to claim 1 , wherein a plurality ofpistons (4) are mounted in expansion chambers (3) and act on the samecam disk or on different cam disks arranged at the same drive shaft(32).
 14. Internal combustion engine according to claim 13 , whereinpistons (4) are provided in pairs so as to work in opposite directions.15. Method for operating an internal combustion engine according toclaim 1 , wherein fuel is ignited in the combustion chamber (1, 1′) andthe drive shaft (32) is driven by the cam gear unit (30, 31), also idlestrokes or stroke pauses in which the piston (4) of the expansionchamber (3) remains at its top dead center and the thrust member (30) ofthe cam gear unit remains raised by the cam disk (31) of the cam gearunit are inserted without ignition of fuel in the combustion chamber (1,1′), wherein the cam disk (31) rotates past the thrust member (30) in anunimpeded manner.
 16. Method according to claim 15 , wherein identicalamounts of fuel are introduced into the combustion chamber (1, 1′) forcarrying out individual explosion strokes.
 17. Method according to claim15 , wherein the fuel in the combustion chamber (1, 1′) is ignited at atime such that, after the fuel in the combustion chamber (1, 1′) isessentially completely burned up, the cam disk (31) has the preciseangular position suitable for the driving of the cam disk (31) by thethrust member (30), whereupon the combustion chamber outlet valve (2,2′) is opened.
 18. Method according to claim 15 , wherein the burnervalve (2, 2′) is opened in a delayed manner at the start of theexpansion stroke of the piston (4), wherein the combustion gas flows outof the combustion chamber (1, 1′) into the expansion chamber (3) inthrottled manner.